Method for making and curing a hydraulic cement mixture

ABSTRACT

The present invention discusses methods for making a cement composition comprising a nanoparticle zeolite. The addition of the nanoparticle zeolite may provide enhanced compressive and tensile strengths, improved rheology, and a change to the cement microstructure. These effects may improve the cement&#39;s use as a cement sheath in drilling operations and under high pressure and high temperature (HPHT) conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of Ser. No. 15/941,350, nowallowed, having a filing date of Mar. 30, 2018.

STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTORS

Aspects of this technology were disclosed in a thesis defense titled,“Evaluation of Nano zeolite as an Additive for Oil-Well Cementing,”presented by Baig, Mirza Talha on May 25, 2017 at King Fahd Universityof Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia, and is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a method of making a cured cementmaterial comprising a nanoparticle-sized zeolite.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Oil and gas production and its exploration influence the world'seconomic structure. Conventional petroleum reservoirs are beingexhausted because of the increase in economic activity in recentdecades. To bridge the gap between supply and demand of petroleumproducts, engineers are now exploring reserves which were neglected inthe past due to various complications associated with extraction.Technological advancements in the field of petroleum engineering havenow enabled researchers to cope with the problems efficiently andimprove the overall success of operations. To exploit the unconventionalresources of petroleum, new techniques must be establishedsimultaneously with an improvement in existing techniques.

In oil and gas wells after drilling the wellbore is completed, a pipestring runs into the wellbore, and a cement slurry is pumped into theannular space between the pipe casing and the formation rock to hold thepipe string in place. This process is referred to as “primarycementing.” The fluid cement slurry hardens as the chemical reactioninvolving the formation of calcium silicate hydrate (CSH) by water, C₃S,C₂S, and C₄AF takes place. The hardened to cement sheath forms a layerseparating the wellbore formation and the casing, which is adheredfirmly to the formation and the casing. The cement in the annular spaceholds the casing in place, and being impermeable, prevents the transportof corrosive fluid from the formation to the casing, thereby precludingthe corrosion of the pipe string. It also provides a barrier thatinhibits the migration of gases in the micro annulus between theformation and the cement, and the cement and pipe casing.

Cementing in high pressure high temperature (HPHT) wells is complicateddue to wide ranging temperature and pressure variations and stresses towhich the annular cement sheath, located between the casing and theformation, is subjected during its service life. The long-term integrityand durability of the annular cement depends on providing casing supportand preventing the migration of formation fluid in liquid or gaseousform through or at the boundaries of the cement sheath. The zonalisolation requires a robust cement slurry which provides a strong anddurable cement-casing and cement-formation bonding, precludes bulkshrinkage by inhibiting the fluid loss, has zero free water settling ofcement, and does not form a micro annulus due to stress imbalance at theinterface resulting from thermal regimes, hydraulic pressure ormechanical stresses. The hardened cement slurry should also resistradial fracturing that may result from shrinkage stresses, thermalexpansion or contraction of the steel casing and pressure fluctuation,mechanical impact, or other conditions within the casing. The HPHT wellshave a larger probability of migration of gas and corrosive fluid andleakage. Therefore, special attention must be paid to cementingprocesses, especially in HPHT wells. Studies have shown thatapproximately 80% of the wells in the Gulf of Mexico have gastransmitted to the surface through the cement casing.

In HPHT formations, the wells are exposed to high temperature variationsthat unsettle the formation as well as the casing, initiating expansionand contraction. In addition, HPHT wells are subjected to high loads inthe lifetime of the well; this may destroy the integrity of cement andmay produce cracks due to compaction loads. Gas migration and strengthretrogression are major challenges in HPHT well cementing.

Gas migration is one of the major failures of primary cementing jobsresulting in loss of production and requires costly remedial cementingjobs to fix the well. One of the major causes behind the Gulf of Mexicooil spill incident was the poor cementing job; in that incident theannulus cement barrier could not stop the flow of hydrocarbons. Someimportant cement properties such as, free water, fluid loss, and staticgel-strength transition time, were not evaluated prior to the cementingjob. See Garg, T., & Gokavarapu, S. (2012). Lessons Learnt from RootCause Analysis of Gulf of Mexico Oil Spill 2010, (December), 10-12,incorporated herein by reference in its entirety. Most HPHT environmentsare in gas production horizons, so it is a major concern in HPHT wellsas gas may migrate through the cement micro cracks. See Shaughnessy, J.,& Helweg, J. (2002). Optimizing HTHP Cementing Operations. IADC/SPEDrilling Conference, 26-28 February, Dallas, Tex. IADC/SPE-74483-MS.DOI: 10.2118/74483-MS, incorporated herein by reference in its entirety.Gas migration causes poor zonal isolation, which in some cases may evenlead to production decline. Therefore, effort must be exercised toachieve effective zonal isolation and prevent fluid migration in thewell. See Boniface, A. (2013). Effects of Thickening Time on theApplication of Cement Slurry for High Pressure/High TemperatureDrilling. 4(3), 32-41, incorporated herein by reference in its entirety.Required cement slurry properties for avoiding gas migration are minimumtransition time, good fluid loss control, minimum free waterdevelopment, and good mechanical properties. See Drecq, P., & Parcevaux,P. (1988). A single technique solves gas migration problems across awide range of conditions. Presented at the International Meeting onPetroleum, Tianjin, China, 1-4 November. SPE-17629-MS. DOI:10.2118/17629-MS, incorporated herein by reference in its entirety.

Strength retrogression, which is the deterioration of cement'scompressive strength at elevated temperatures, is particularly common inhigh temperature wells. See Iverson, B., Maxson, J., & Bour, D. (2010).Strength Retrogression in Cements Under High Temperature Conditions.Proceeding: Thirty-Fifth Workshop on Geothermal Reservoir Engineering,incorporated herein by reference in its entirety. As the wellboretemperature exceeds 230 OF, cement strength starts to decreasegradually. Calcium Silicate Hydrate (CSH) gel, which is formed by thehydration of cement and gives cement the strength, is stable up to 230°F. Above 230 OF, CSH gel converts to alpha dicalcium silicate hydrate(α-C2SH). See Gaurina-Medimurec, N., N., Matanovit, D., & Krklec, G.(1994). Cement slurries for geothermal wells cementing.Rudarsko-Geoloiko-Naftni Zbomik, 6(1), 127-134, incorporated herein byreference in its entirety. α-C2SH is crystalline and denser than CSH,which causes shrinkage in set cement, causing microcracks and therebyincreasing permeability. The formation of α-C2SH from CSH also causesthe phenomenon of strength retrogression in HPHT wells. See Eilers, L.H. and Root, R. L. (1976). Long-Term Effects of High Temperature onStrength Retrogression of Cements. Presented at the SPE CaliforniaRegional Meeting, long Beach, Calif., 7-9 April. SPE-5871-MS DOI:10.2118/581-MS; and Jupe, A. C., Wilkinson, A. P., Luke, K., &Funkhouser, G. P. (2008). Class H cement hydration at 180° C. and highpressure in the presence of added silica. Cement and Concrete Research,38(5), 660-666. DOI: 10.1016/j.cemconres.2007.12.004, each incorporatedherein by reference in their entirety.

Nanotechnology is one of the most dynamic research areas rich with bothinnovative science and valuable applications. At nano-scale, theproperties of an engineered nanomaterial are different from that of amacro-material having the same chemical composition. Nanomaterials havea larger surface area when compared to an equal mass of the samematerial in macro form. See Caskey, L. C., Carolina, N., Kolbash, C., &Carolina, N. (2015). Nanomaterials: The Good, the Bad, and the Ugly,(677), incorporated herein by reference in its entirety. Nanotechnologyhas provided a wide variety of solutions to resolve industrial problems,which could not be previously addressed by customary methods. It enablesresearchers to alter properties of bulk materials at the nanometerscale. Various nanomaterials have been successfully applied in manyareas of petroleum engineering, especially in drilling fluids, losscirculation, enhanced oil recovery (EOR), and cementing.

Various types of nano silica have been reported to increase compressivestrength, enhance early compressive strength, reduce permeability andporosity, improve fluid loss, reduce transition time from 100 lb/ft² to500 lb/ft, and decrease density segregation. See Ershadi, V., Ebadi, T.,Rabani, A., Ershadi, L., & Soltanian, H. (2011). The Effect of Nanosilica on Cement Matrix Permeability in Oil Well to Decrease thePollution of Receptive Environment. International Journal ofEnvironmental Science and Development, 2(2), 128-132; Patil, R., &Deshpande, A. (2012). Use of Nanomaterials in Cementing Applications.Presented at SPE International Oilfield Nanotechnology Conference andExhibition, Noordwijk, 12-14 June. SPE-155607-MS. DOI:10.2118/155607-MS; and Rahman M. K., Amer S. A., Al-Majed A. A., (2014).Portland Saudi Cement Type-G with Nano Silica Additive for HighPressure-High Temperature Applications. US Patent ApplicationPublication, No. 2014-0332217; each incorporated herein by reference intheir entirety. SEM images of cement mix with nanosilica confirmednanofiller properties of nanosilica for denser microstructure. Pang etal. observed that the lower particle size and the higher aspect ratiosresulted in increased cement hydration, which improved compressivestrength. See Pang, X., Boul, P. J., & Jimenez, W. C. (2014). IADC/SPE168037 Nano silica as Accelerators in Oilwell Cementing at LowTemperatures, (March), 4-6, incorporated herein by reference in itsentirety. Carbon nanotubes have also been tested as an additive in oilwell cementing to improve early compressive strength development, finalcompressive strength, and tensile strength with only a smallconcentration. See De Paula, J. N., Calixto, J. M., Ladeira, L. O.,Ludvig, P., Souza, T. C. C., Rocha, J. M., & de Melo, E. A. A. V.(2014). Mechanical and rheological behavior of oil-well cement Slurriesproduced with clinker containing carbon Nanotubes. Journal of PetroleumScience and Engineering, 122, 274-279. DOI:10.1016/j.petrol.2014.07.020; and Khan, W. A., Rahman, M. K., Mahmoud,M. A., & Sarmah, P. (2016). MWCNT for Enhancing Mechanical Properties ofOil Well Cement for HPHT Applications, each incorporated herein byreference in their entirety. Nanoclay has also been investigated as anadmixture for oil well cementing at HPHT. See Murtaza, M., Rahman, M.K., & AI-Majed, A. A. (2016). Mechanical and Microstructural Studies ofNanoclay Based Oil Well Cement Mix under High Pressure and TemperatureApplication. International Petroleum Technology Conference. DOI:10.2523/IPTC-18991-MS, incorporated herein by reference in its entirety.It was observed that nano clay not only accelerated the early strengthdevelopment, but also increased the final strength along with areduction in permeability and porosity of hardened cement. Smallernanoclay size aided in filling the capillaries and resulted in densemicrostructure.

Zeolite is an excellent supplementary cementitious material because ofits high pozzolanic reactivity. See Ahmadi, B., & Shekarchi, M. (2010).Use of natural zeolite as a supplementary cementitious material. Cementand Concrete Composites, 32(2), 134-141. DOI:10.1016/j.cemconcomp.2009.10.006, incorporated herein by reference inits entirety. Pozzolanic materials react with the calcium hydroxideproduced during the hydration of ordinary Portland cement. See Massazza,F. (2003). Pozrolana and Pozzolanic Cements. Lea's Chemistry of Cementand Concrete, 15(1993), 471-635. DOI: 10.1016/B978-075066256-7/50022-9,incorporated herein by reference in its entirety. The term ‘pozzolanicactivity’ refers to all reactions taking place between the pozzolans,lime, and water. Natural pozzolans react with lime, which results in theformation of calcium silicate hydrate (C—S—H), and calcium aluminatehydrates. Jana observed the reduction of calcium hydroxide produced inPortland cement with the addition of zeolite, which confirms thepozzolanic behavior of zeolite. See Jana, D. (2007). A new look to anold pozzolan: clinoptilolite—a promising pozzolan in concrete.Proceedings of the Twenty-Ninth Conference on Cement Microscopy, QuebecCity, PQ, Canada, 20-24 May 2007, incorporated herein by reference inits entirety. Cannon investigated the effect of size and quantity ofzeolite of various types as cement replacement material. It was observedthat as the particle size of zeolite was reduced, compressive strengthof the cement increased and free water reduced. See Cannon, J. (2013).Well Cement Containing Zeolite Minerals for HPHT Applications. DOI:10.2118/134422, incorporated herein by reference in its entirety.

The present disclosure relates to a type of nanomaterial, referred to asnano zeolite, which improves the properties of cement in oil/gas wellssubjected to HPHT conditions. A well located in Saudi Arabia was used totest a cement mix design. Nano zeolite material was added at variouspercentages to a Saudi Class G cement, and the beneficial impact of nanozeolite on the strength, rheological, and durability properties of thecement slurry was demonstrated.

In view of the foregoing, one objective of the present invention is toprovide a method for making a cured cement material comprising zeoliteparticles as an additive for improved properties.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a methodof making a cured cement material. The method involves the steps ofmixing a hydraulic cement, water and/or brine, and zeolite nanoparticlesto form a wet cement slurry. The water and/or brine is mixed in anamount of 40-50% by weight of the hydraulic cement and the zeolitenanoparticles are mixed in an amount of 0.5-4 wt % by weight of thehydraulic cement. The zeolite nanoparticles have an average diameter of40-100 nm. The wet cement slurry is cured to produce the cured cementmaterial, which comprises zeolite clusters having an average clusterdiameter of 1-12 μm.

In one embodiment, the cured cement material further comprises pores,and a subset of the zeolite clusters is located within the pores.

In one embodiment, the hydraulic cement is selected from the groupconsisting of an API Class A Portland cement, an API Class G Portlandcement, an API Class H Portland cement, and a Saudi Class G hydrauliccement.

In one embodiment, the zeolite nanoparticles have a silica to aluminamass ratio of 1.2:1-3.0:1.

In one embodiment, the zeolite nanoparticles comprise 1-6 wt % CaOrelative to a total weight of the zeolite nanoparticles.

In one embodiment, the wet cement slurry reaches a compressive strengthof 2,000 psi within a time of curing which is 0.8-3.0 h faster than anessentially identical wet cement slurry that was not formed with zeolitenanoparticles.

In one embodiment, the wet cement slurry is cured between a casing and aformation of a well bore.

In one embodiment, the wet cement slurry further comprises silica flour.

In a further embodiment, the wet cement slurry further comprises atleast one additive selected from the group consisting of an expandingagent, a dispersant, a fluid loss control agent, a retarder, a defoamer,a density reducing additive, a density enhancing weighting agent, afoaming agent, and a friction reducing agent.

In a further embodiment, where the wet cement slurry further comprisessilica flour and at least one additive, the cured cement material has acompressive strength of 5,500-6,800 psi.

In a further embodiment, where the wet cement slurry further comprisessilica flour and at least one additive, the wet cement slurry reaches acompressive strength of 2,000 psi within a time of curing which is1.5-3.5 h faster than an essentially identical wet cement slurry thatwas not formed with zeolite nanoparticles.

In one embodiment, the cured cement material has a weight of calciumsilicate hydrate that is 20-70% lower than a second weight of calciumsilicate hydrate of an essentially identical cured cement material madefrom a wet cement slurry that does not contain zeolite nanoparticles,relative to the second weight.

In one embodiment, the cured cement material has a weight of calciumhydroxide that is greater by a factor of 1.5-3.0 than a second weight ofcalcium hydroxide of an essentially identical cured cement material madefrom a wet cement slurry that does not contain zeolite nanoparticles.

According to a second embodiment, the present disclosure relates to acured cement material comprising a cured hydraulic cement and zeoliteclusters having an average cluster diameter of 1-12 μm. The zeoliteclusters comprise zeolite particles having an average diameter of400-600 nm.

In one embodiment, the cured cement material further comprises calciumsilicate hydrate (CSH) at a weight percentage of 1-20 wt % relative to atotal weight of the cured cement material.

In one embodiment, the cured cement material further comprises calciumhydroxide (CH) at a weight percentage of 35-55 wt % relative to a totalweight of the cured cement material.

In one embodiment, the cured cement material further comprises calciumsilicate at a weight percentage of 15-35 wt % relative to a total weightof the cured cement material.

In one embodiment, the cured cement material is located between a casingand a formation of a well bore.

In one embodiment, the cured cement material has pores, and the zeoliteclusters are located within a subset of the pores.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a TEM image of a nano zeolite.

FIG. 2 is a particle size distribution of a nano zeolite.

FIG. 3 is a graph of the compressive strength of the G, G1, G2, and G3slurry mixes over time.

FIG. 4 is a graph of the compressive strength of the BM, NZ1, NZ2, andNZ3 slurry mixes over time.

FIG. 5 is a graph of the consistency of BM, NZ1, NZ2, and NZ3 slurrymixes over time for the determination of thickening time.

FIG. 6A is an SEM image of the G mix cured at HPHT for 24 hours.

FIG. 6B is an SEM image of the G1 mix cured at HPHT for 24 hours.

FIG. 6C is an SEM image of the G2 mix cured at HPHT for 24 hours.

FIG. 7A is an SEM image with higher magnification of the G1 mix cured atHPHT for 24 hours.

FIG. 7B is an SEM image with higher magnification of the G1 mix cured atHPHT for 24 hours.

FIG. 7C is the EDS from the Spectrum 18 region in FIG. 7B.

FIG. 7D is the EDS from the Spectrum 20 region in FIG. 7B.

FIG. 7E is an SEM image of nano zeolites.

FIG. 7F is a magnified SEM image of the G2 mix after curing at HPHT for24 hours.

FIG. 8A is an SEM image of the G3 mix.

FIG. 8B is the EDS from the Spectrum 36 region in FIG. 8A.

FIG. 8C is the EDS from the Spectrum 37 region in FIG. 8A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown.

The present disclosure will be better understood with reference to thefollowing definitions. As used herein, the words “a” and “an” and thelike carry the meaning of“one or more.” Within the description of thisdisclosure, where a numerical limit or range is stated, the endpointsare included unless stated otherwise.

As used herein, the words “about,” “approximately,” or “substantiallysimilar” may be used when describing magnitude and/or position toindicate that the value and/or position described is within a reasonableexpected range of values and/or positions. For example, a numeric valuemay have a value that is +/−0.1% of the stated value (or range ofvalues), +/−1% of the stated value (or range of values), +/−2% of thestated value (or range of values), +/−5% of the stated value (or rangeof values), +/−10% of the stated value (or range of values), +/−15% ofthe stated value (or range of values), or +/−20% of the stated value (orrange of values). Within the description of this disclosure, where anumerical limit or range is stated, the endpoints are included unlessstated otherwise. Also, all values and subranges within a numericallimit or range are specifically included as if explicitly written out.

As used herein, “compound” is intended to refer to a chemical entity,whether as a solid, liquid, or gas, and whether in a crude mixture orisolated and purified.

As used herein, “composite” refers to a combination of two or moredistinct constituent materials into one. The individual components, onan atomic level, remain separate and distinct within the finishedstructure. The materials may have different physical or chemicalproperties, that when combined, produce a material with characteristicsdifferent from the original components. In some embodiments, a compositemay have at least two constituent materials that comprise the sameempirical formula but are distinguished by different densities, crystalphases, or a lack of a crystal phase (i.e. an amorphous phase).

The present disclosure is intended to include all hydration states of agiven compound or formula, unless otherwise noted or when heating amaterial. For example, aluminum sulfate, Al₂(SO₄)₃, includes anhydrousAl₂(SO₄)₃, Al₂(SO₄)₃.18H₂O, and any other hydrated forms or mixtures.

In addition, the present disclosure is intended to include all isotopesof atoms occurring in the present compounds and complexes. Isotopesinclude those atoms having the same atomic number but different massnumbers. By way of general example, and without limitation, isotopes ofhydrogen include deuterium and tritium. Isotopes of carbon include ¹³Cand ¹⁴C. Isotopes of nitrogen include ¹⁴N and ¹⁵N. Isotopes of oxygeninclude ¹⁶O, ¹⁷O, and ¹⁸O. Isotopes of silicon include ²⁸Si, ²⁹Si, and³⁰Si. Isotopically-labeled compounds of the disclosure may generally beprepared by conventional techniques known to those skilled in the art orby processes analogous to those described herein, using an appropriateisotopically-labeled reagent in place of the non-labeled reagentotherwise employed.

According to a first aspect, the present disclosure relates to a methodof making a cured cement material. The method involves the steps ofmixing a hydraulic cement, water and/or brine, and zeolite nanoparticlesto form a wet cement slurry.

As used herein, the term or phrase “cement” refers to a composition orsubstance with one or more constituents that is capable of bindingmaterials together, once set. Generally, cement may include a number ofdry constituents chosen based on the desired ratio or class of cement tobe produced. Thus, cement refers to the dry, pre-set composition unlessthe context clearly dictates otherwise, for example, in a wet cementslurry, or in a cured cement material. In one embodiment, the cement mayinclude hydraulic cement, non-hydraulic cement, or a combinationthereof. In a preferred embodiment, the cement comprises Portlandcement, a basic ingredient of concrete, mortar, stucco, andnon-specialty grout, which is a fine powder, produced by heatinglimestone and clay minerals in a kiln to form clinker, grinding theclinker, and adding small amounts of other materials. Several types ofPortland cement may be employed herein, for example, API Class A, ClassG, or Class H; Ordinary Portland Cement (OPC) type I, type II, type III,type IV, or type V; or a combination thereof (in accordance with theASTM CI50 standard). Portland Cement type Ia, type IIa, and/or type IIIamay also be used, which have the same composition as types I, II, andIII except that an air-entraining agent is ground into the mix (also inaccord with the ASTM C150 standard).

Additional cement types include hydraulic cements, Saudi Class Ghydraulic cement, non-hydraulic cements, Portland fly ash cement,Portland Pozzolan cement, Portland silica fume cement, masonry cements,mortars, EMC cements, stuccos, plastic cements, expansive cements, whiteblended cements, Pozzolan-lime cements, slag-lime cements, supersulfatedcements, calcium aluminate cements, calcium sulfoaluminate cements,geopolymer cements, Rosendale cements, polymer cement mortar, limemortar, and/or pozzolana mortar. In one embodiment, the cement comprisesa cement blend of two or more types of cement, for example, a blendcomprising Portland cement and non-Portland hydraulic cement. In afurther embodiment, the cement is in the dry form. If needed to set,water is typically added after the cement is mixed with the othercomponents/ingredients, for example, the date palm ash, and the coarseand fine aggregate, and it is then ready to be hardened or set. In oneembodiment, the hydraulic cement is selected from the group consistingof an API Class A Portland cement, an API Class G Portland cement, anAPI Class H Portland cement, and a Saudi Class G hydraulic cement.

Typically, hydraulic cements, particularly Portland cements, are used tocement the well casing within the well bore. Hydraulic cements set anddevelop compressive strength due to the occurrence of a hydrationreaction which allows them to set or cure under water. The physicalproperties of the set cement relate to the crystalline structure of thecalcium-silicate-hydrates formed during hydration. For example,conventional Portland cements form an interlocking crystalline networkof, for example, tricalcium silicate, dicalcium silicate, tetracalciumaluminum ferrite and calcium hydroxide crystals. These crystalsinterconnect to form an interlocking crystalline structure whichprovides both flexural strength and a degree of resiliency. Hydrationproducts of Portland cements may also form crystalline or amorphousinterlocking networks of the hydration products calcium silicate hydrate(CSH, or C—S—H), calcium hydroxide (CH, or Portlandite), calciumsilicate (Lamnite), aluminum calcium iron oxide (such as Ca₂FeAlO₅),and/or silicon dioxide.

Cements suitable for use in a wet cement slurry include materials withhydraulic properties, such as hydraulic cement, slag and blends ofhydraulic cement and slag (slagment), which are well known in the art.The term “hydraulic cement” refers to any inorganic cement that hardensor sets due to hydration. As used herein, the term“hydraulically-active” refers to properties of a cement material thatallow the material to set in a manner like hydraulic cement, either withor without additional activation. Hydraulically-active cement materialsmay also have minor amounts of extenders such as bentonite, gilsonite,and cement materials used either without any appreciable sand oraggregate material or admixed with a granular filling material such assand, ground limestone, the like. Strength enhancers such as silicapowder or silica flour may also be employed. Hydraulic cements, forinstance, include Portland cements, aluminous cements, pozzolan cements,fly ash cements, and the like. Thus, for example, any of the oil welltype cements of the class “A-H” as listed in the API Spec 10, (1st ed.,1982), are suitable hydraulic cements. In addition, the cement materialmay include silica sand/flour and/or weighing agents including hematiteor barite.

To form the wet cement slurry, the zeolite nanoparticles are mixed in anamount of 0.5-4 wt %, preferably 1.0-3.5 wt %, more preferably 1.5-3.2wt %, even more preferably 1.8-2.5 wt % by weight of the hydrauliccement. However, in some embodiments, zeolite nanoparticles are mixed inan amount of less than 0.5 wt % or greater than 4.0 wt % by weight ofthe hydraulic cement. In an alternative embodiment, the wet cementslurry may be substantially free of zeolite nanoparticles, meaning thatthe wet cement slurry may comprise less than 0.001 wt %, preferably lessthan 0.0001 wt %, or about 0 wt % zeolite nanoparticles. In oneembodiment, the zeolite nanoparticles may be referred to as “nanozeolite.”

Zeolites are porous aluminosilicate minerals that may be found in natureor synthesized. Elementary building units of zeolites are SiO₄ and AlO₄tetrahedra. Adjacent tetrahedra are linked at their corners via a commonoxygen atom, which results in an inorganic macromolecule with athree-dimensional framework. The three-dimensional framework of azeolite also comprises channels, channel intersections, and/or cageshaving dimensions in the range of 0.1-10 nm, preferably 0.2-5 nm, morepreferably 0.2-2 nm. Water molecules may be present inside thesechannels, channel intersections, and/or cages.

In one embodiment, the zeolite nanoparticles may comprise one or morezeolites with a zeolite framework of, or similar to, amicite,ammonioleucite, analcime, barrerite, brewsterite, beilbergite,bikitaite, boggsite, chabazite, chiavennite, clinoptilolite, cowlesite,dachiardite, edingtonite, epistilbite, erionite, faujasite, ferrierite,garronite, gaultite, gismondine, gmelinite, gobbinsite, gonnardite,goosecreekite, gottardiite, harmotome, heulandite, hsianghualite,kalborsite, laumontite, leucite, lévyne, lovdarite, marciopaite,mazzite, merlinoite, mesolite, montesommaite, mordenite, mutinaite,nabesite, natrolite, offrietite, pahasapaite, paranatrolite, parthéite,paulingite, perlialite, phillipsite, pollucite, roggianite, scolecite,stellerite, stilbite, terranovaite, tetranatrolite, thomsonite,tschemichite, tschörtnerite, tvedalite, wairakite, weinebeneite,willhendersonite, yugawaralite, and combinations thereof. In anotherembodiment, the zeolite may have a zeolite framework similar to asynthetic crystalline aluminosilicate, such as zeolites having thetrademarked names of ZEOLITE A, ZEOLITE X, ZEOLITE Y, ZEOLITE K-G,ZEOLITE ZK5, ZEOLITE BETA, ZEOLITE ZK-4, SAPO, ALPO, USY, ZEOLITE ZSM-5(“ZEOLITES SOCONY MOBIL-5” also called more simply, ZSM-5), ZSM-11,ZSM-12, ZSM-20, ZSM-23, ZSM-35, ZSM-38, ZSM-50, and combinationsthereof. In an alternative embodiment, some other compositionallyrelated material that is not a zeolite may be used in place of thezeolite nanoparticles, such as amorphous silica-alumina. In oneembodiment, the zeolite nanoparticles may be considered as a pozzolan.

In one embodiment, the zeolite nanoparticles may comprise a zeolitehaving the formula M_(a/n)[(AlO₂)₂(SiO₂)_(b)].xH₂O, with M representinga metal such as Na, K, Li, Ag, Ca, Ba, Fe, or some other metal, and xrepresenting the water molecules incorporated into the zeolite.

In one embodiment, the zeolite nanoparticles have a weight percentage ofsilica (SiO₂) of 50-70 wt %, preferably 55-65 wt %, more preferably59-63 wt %, or about 61 wt %, relative to a total weight of the zeolitenanoparticles. However, in some embodiments, the zeolite nanoparticlesmay have a weight percentage of silica of less than 50 wt % or greaterthan 70 wt %.

In one embodiment, the zeolite nanoparticles may comprise alumina(Al₂O₃) at a weight percentage of 20-40 wt %, preferably 25-35 wt %,more preferably 28-32 wt %, or about 30 wt % relative to a total weightof the zeolite nanoparticles. However, in some embodiments, the zeolitenanoparticles may comprise alumina at a weight percentage smaller than20 wt % or larger than 40 wt %.

In one embodiment, the zeolite nanoparticles have a silica (SiO₂) toalumina (Al₂O₃) mass ratio of 1.2:1-3.0:1, preferably 1.5:1-2.8:1, morepreferably 1.8:1-2.5:1, or about 2.0:1. However, in some embodiments,the silica to alumina mass ratio may be lower than 1.2:1 or greater than3.0:1.

In one embodiment, the zeolite nanoparticles may comprise iron(III)oxide (Fe₂O₃) at a weight percentage of 0.2-2.5 wt % o, preferably0.5-1.8 wt %, more preferably 1.0-1.5 wt %, or about 1.2 wt % relativeto a total weight of the zeolite nanoparticles. However, in someembodiments. the zeolite nanoparticles may comprise iron(III) oxide(Fe₂O₃) at a weight percentage smaller than 0.2 wt % or larger than 2.5wt %. In other embodiments, the zeolite nanoparticles may compriseiron(II) oxide (FeO). In some embodiments, the zeolite nanoparticles maycomprise substantially no Fe, for instance, less than 0.01 wt % Fe,preferably less than 0.001 wt % Fe, or about 0 wt % Fe, relative to atotal weight of the zeolite nanoparticles.

In one embodiment, the zeolite nanoparticles comprise 1-6 wt % CaO,preferably 2-5 wt % CaO, more preferably 3-4.8 wt % CaO, relative to atotal weight of the zeolite nanoparticles. However, in otherembodiments, the zeolite nanoparticles may comprise less than 1 wt % CaOor greater than 6 wt % CaO, relative to a total weight of the zeolitenanoparticles. In some embodiments, the zeolite nanoparticles maycomprise substantially no Ca, for instance, less than 0.01 wt % Ca,preferably less than 0.001 wt % Ca, or about 0 wt % Ca, relative to atotal weight of the zeolite nanoparticles.

In one embodiment, the zeolite nanoparticles have an average diameter of40-100 nm, preferably 45-80 nm, more preferably 60-75 nm, though in someembodiments, the zeolite nanoparticles may have an average diameter ofless than 40 nm or greater than 100 nm. For instance, zeolitemicroparticles or millimeter-sized particles may be used. The zeolitenanoparticles may have a spherical shape, or may be shaped likecylinders, boxes, spikes, flakes, plates, ellipsoids, toroids, stars,ribbons, discs, rods, granules, prisms, cones, flakes, platelets,sheets, or some other shape.

In one embodiment, the zeolite nanoparticles may be substantiallyspherical, meaning that the distance from the particle centroid (centerof mass) to anywhere on the nanoparticle outer surface varies by lessthan 30%, preferably by less than 20%, more preferably by less than 10%of the average distance.

In one embodiment, the zeolite nanoparticles are monodisperse, having acoefficient of variation or relative standard deviation, expressed as apercentage and defined as the ratio of the particle diameter standarddeviation (c) to the particle diameter mean (p), multiplied by 100%, ofless than 25%, preferably less than 10%, preferably less than 8%,preferably less than 6%, preferably less than 5%. In a preferredembodiment, the zeolite nanoparticles are to monodisperse having aparticle diameter distribution ranging from 80% of the average particlediameter to 120% of the average particle diameter, preferably 85-115%,preferably 90-110% of the average particle diameter. In anotherembodiment, the zeolite nanoparticles are not monodisperse.

In one embodiment, the wet cement slurry comprises silica flour at aweight percentage of 25-45 wt %, preferably 30-40 wt %, preferably 32-37wt %, or about 35 wt % relative to a total weight of the hydrauliccement. However, in some embodiments, the wet cement slurry may compriseless than 25 wt %, or greater than 45 wt % silica flour. The silicaflour may comprise particles (or sand) of crystalline SiO₂, preferablyα-quartz, having diameters of 1-300 μm, preferably 5-250 μm, morepreferably 25-200 μm. Preferably the silica flour comprises greater than95 wt % SiO₂, preferably greater than 98 wt % SiO₂, more preferablygreater than 99 wt % SiO₂. In other embodiments, silica flour may bereferred to as silica sand, silica powder, or quartz sand. In analternative embodiment, the wet cement slurry may comprise silica in adifferent form, including but not limited to fumed silica, amorphoussilica, and β-quartz. In another alternative embodiment, the wet cementslurry may comprise desert sand or some other naturally occurring sandin place of the silica flour.

In one embodiment, the wet cement slurry does not comprise cement kilndust, vitrified shale, and/or amorphous silica. In another embodiment,the wet cement slurry does not comprise nanoclay. As defined here,nanoclays are nanoparticles of layered mineral silicates, and may belongto classes such as montmorillonite, bentonite, kaolinite, hectorite, andhalloysite. In a further embodiment, the wet cement slurry does notcomprise any layered mineral silicates as nanoparticles or in otherforms.

In one embodiment, the wet cement slurry comprises at least one additiveselected from the group consisting of an expanding agent, a dispersant,a fluid loss control agent, a retarder, a defoamer, a density reducingadditive, a density enhancing weighting agent, a foaming agent, afriction reducing agent, a suspending agent, a viscosifier, and aplasticizer. The amount of additive typically is dependent on the typeof hydraulic cement used and desired density of the wet cement slurry.One or more additives may be present in the cement at a weightpercentage of 0.1-3.0 wt %, preferably 0.2-2.5 wt %, more preferably0.5-1.8 wt % by weight of the hydraulic cement. However, in someembodiments, less than 0.1 wt % or greater than 3.0 wt % of cementadditive by weight of the hydraulic cement, may be present.

Examples of retarders are lignin and sugar derivatives. Deflocculents ordispersants to control fluidity include lignosulfonates, naphthalenesulfonates, phenol sulfonates, phosphates, phosphonates, sulfonatedstyrene maleic anhydride, sulfonated styrene, maleimide, polyacrylatesand polymethacrylates. Viscosity reducers include organic acids.

The wet cement slurry of the invention may further contain a suspendingagent for maintaining the slurry with minimal separation of the slurrycomponents. Certain types of suspending agents of the type used in thedrilling mud industry may be used for the purposes of the presentinvention. Suitable suspending/thixotropic agents include welan gum,xanthan gum, cellulose, polyanionic cellulose, xanthan gums, celluloseand derivatives such as carboxymethyl-hydroxyethyl-cellulose, guar andits derivatives, starch and polysaccharides, succinoglycan, polyethyleneoxide, bentonite, attapulgite, mixed metal hydroxides, clays such asbentonite and attapulgite, mixed metal hydroxides, oil in wateremulsions created with paraffin oil and stabilized with ethoxylatedsurfactants, poly (methyl vinyl ether/maleic anhydride) decadienecopolymer, etc. Preferred suspending agents include iota carrageenan andpoly (methyl vinyl ether/maleic anhydride) decadiene copolymer.

In one embodiment, water and/or brine may be mixed in the wet cementslurry in an amount of 40-50% by weight of the hydraulic cement,preferably 41-48% by weight of the hydraulic cement, more preferably42-47% by weight of the hydraulic cement, even more preferably 43-46% byweight of the hydraulic cement. In general, the amount of water and/orbrine used in forming the wet cement slurry depends upon the type ofhydraulic cement selected and the job conditions at hand. Thus, in otherembodiments, the water and/or brine may be mixed in the wet cementslurry in an amount of less than 40% or greater than 50% by weight ofthe hydraulic cement. The amount of water used may vary over a widerange, depending upon such factors as the required consistency of thewet cement slurry and upon the strength requirement for a particularwell bore. In one embodiment, the water and/or brine may comprise theabove-mentioned additives before being added to the dry ingredients ofthe cement mixture.

The water and/or brine may be seawater or freshwater, and may be takenfrom a natural source, such as an aquifer, lake, or ocean, and may befiltered to remove large solids before being mixed. A brine is anaqueous mixture of one or more soluble salts, such as sodium chloride,potassium chloride, calcium chloride, calcium bromide, sodium bromide,potassium bromide, or zinc bromide, and has at least 30 g soluble saltsper L solution. Sea water or water from a salt lake may be considered abrine, or a brine may be formed by mixing water or freshwater withsoluble salts or a solution comprising soluble salts.

In one embodiment the wet cement slurry may comprise only water, cement,and zeolite nanoparticles. For instance, the wet cement slurry maycomprise an amount of cement, and 38-50 wt % water, preferably 46-48 wt% water; and 0.5-3.0 wt % zeolite nanoparticles, preferably 1.5-2.5 wt %zeolite nanoparticles, where each weight percentage is relative to atotal weight of the cement.

In another embodiment, the wet cement slurry may comprise cement, water,silica flour, expanding agent, dispersant, a first fluid loss controlagent, a second fluid loss control agent, a retarder, and the zeolitenanoparticles. For instance, this wet cement slurry may comprise anamount of cement; 38-50 wt %, preferably 42-48 wt % water; 20-40 wt %/o,preferably 30-38 wt % silica flour; 0.1-3.0 wt %, preferably 0.8-1.2 wt% expanding agent; 0.1-3.0 wt %, preferably 0.8-1.2 wt % dispersant;0.05-0.50 wt %, preferably 0.10-0.30 wt % of a first fluid loss controlagent; 0.1-0.8 wt %, preferably 0.2-0.7 wt % of a second fluid losscontrol agent; 0.3-1.0 wt %, preferably 0.5-0.8 wt % retarder; and0.5-3.5 wt % zeolite nanoparticles, preferably 1.5-2.5 wt % zeolitenanoparticles, where each weight percentage is relative to a totalweight of the cement.

The wet cement slurry may have a density of 14.0-18.0 lb/gal, preferably15.0-17.0 lb/gal, more preferably 15.8-16.9 lb/gal.

After the wet cement slurry is formed, the wet cement slurry is cured toproduce the cured cement material. In one embodiment, the wet cementslurry is cured between a casing and a formation of a well bore, thusproducing a cured cement material between the casing the formation ofthe well bore. The wet cement slurry may be cured at a temperaturesimilar to that within a well bore, such as 150-350° F., preferably180-320 OF, more preferably 190-290° F., even more preferably 220-260°F. However, in some embodiments, the wet cement slurry may be cured at atemperature of less than 150° F. or greater than 350° F. In oneembodiment, the wet cement slurry may be cured around room temperature,for instance, 68-78° F.

In one embodiment, the wet cement slurry may be cured at a pressure of5,000-10,000 psi, preferably 6,000-9,000 psi, more preferably7,000-8,500 psi. However, in some embodiments, the wet cement slurry maybe cured at atmospheric pressure, or may be cured at pressures lowerthan 5,000 psi or greater than 10,000 psi.

In one embodiment, the wet cement slurry may be cured following theaddition of an activator. Activators and activation methods as describedin U.S. Pat. Nos. 5,447,197 and 5,547,506 may be employed, including“over-activation.” Activators are typically added just prior to use of astorable cement slurry. Typical activators include, but are not limitedto, solutions of Group IA and IIA hydroxides and carbonates, such assodium hydroxide (caustic), potassium hydroxide, magnesium hydroxide,calcium hydroxide, sodium carbonate and calcium carbonate; Group IAhalides, such as sodium fluoride and KF; ammonium halides, such asammonium fluoride and ammonium bifluoride (ABF); sulfates, such assodium sulfate; aluminates, such as sodium aluminate and potassiumaluminate; carbonates, such as alkali carbonates, like sodium carbonate;phosphates, such as dibasic alkali phosphates (like dibasic potassiumphosphate) and tribasic alkali phosphates (like tribasic potassiumphosphate); ammonium phosphates, such as tribasic ammonium phosphate anddibasic ammonium phosphate; silicates; and amines (such astriethanolamine (“TEA”), diethanolamine, etc. Most typical activatorsare alkali silicates, such as sodium silicates. For slag slurries asodium silicate “Crystal 120H,” Crosfield, Warrington, England, with aparticular silica/soda ratio is especially preferred. Sodium silicate(“Crystal 100S”, Crosfield) with a different silica/soda ratio isespecially preferred for hydraulic cement and slagment slurries. In oneembodiment, an activator is added just prior to pumping the cement intoa well bore to form a cured cement between a formation and a casing. Acured cement located between a formation and a casing may be consideredas a cement sheath.

In one embodiment, a wet cement slurry may have a plastic viscosity of60-120 cp, preferably 75-110 cp, more preferably 80-105 cp, or about 100cp. However, in some embodiments, the wet cement slurry may have aplastic viscosity of less than 60 cp or greater than 120 cp. In oneembodiment, increasing a concentration of zeolite nanoparticles in thewet cement slurry may increase the plastic viscosity, for instance, fromabout 70 cp to about 100 cp.

In one embodiment, a wet cement slurry further comprising silica flourand at least one additive may have a plastic viscosity of 230-300 cp,preferably 250-290 cp, more preferably 265-280 cp, or about 275 cp.However, in some embodiments, the wet cement slurry may have a plasticviscosity of less than 230 cp or greater than 300 cp. In one embodiment,increasing a concentration of zeolite nanoparticles in the wet cementslurry may increase the plastic viscosity.

In one embodiment, a wet cement slurry may have a yield point of 15-30lb/100 ft², preferably 20-28 lb/100 ft², more preferably 22-27 lb/100ft², or about 25 lb/100 ft². In one embodiment, increasing aconcentration of zeolite nanoparticles in the wet cement slurry mayincrease the yield point, for instance, from about 20 lb/100 ft² toabout 25 lb/100 ft².

In one embodiment, a wet cement slurry further comprising silica flourand at least one additive may have a yield point of 3-9 lb/100 ft²,preferably 3.5-8 lb/100 ft², or about 4 lb/100 ft², or about 7 lb/100ft². In one embodiment, increasing a concentration of zeolitenanoparticles in the wet cement slurry may increase the yield point.

In one embodiment, a wet cement slurry may have a 10-sec gel strength of15-25 lb/100 ft², preferably 16-23 lb/100 ft², or about 21 lb/100 ft².In one embodiment, increasing a concentration of zeolite nanoparticlesin the wet cement slurry may increase the 10-sec gel strength, forinstance, from about 16 lb/100 ft² to about 21 lb/100 ft².

In one embodiment, a wet cement slurry further comprising silica flourand at least one additive may have a 10-sec gel strength of 4-9 lb/100ft², or 6-7 lb/100 ft². In one embodiment, increasing a concentration ofzeolite nanoparticles in the wet cement slurry may increase the 10-secgel strength, for instance, from about 6 lb/100 ft² to about 7 lb/100ft².

In one embodiment, a wet cement slurry may have a 10-min gel strength of50-100 lb/100 ft², preferably 70-95 lb/100 ft², more preferably 80-90lb/100 ft², or about 88 lb/100 ft². In one embodiment, increasing aconcentration of zeolite nanoparticles in the wet cement slurry mayincrease the 10-min gel strength, for instance, from about 50 lb/100 ft²to about 90 lb/100 ft².

In one embodiment, a wet cement slurry further comprising silica flourand at least one additive may have a 10-min gel strength of 15-30 lb/100ft², preferably 20-29 lb/100 ft², more preferably 22-28 lb/100 ft², orabout 25 lb/100 ft². In one embodiment, increasing a concentration ofzeolite nanoparticles in the wet cement slurry may increase the 10-mingel strength, for instance, from about 20 lb/100 ft² to about 25 lb/100ft².

The wet cement slurry may be left to cure for a length of time necessaryto achieve a desired mechanical property, such as a desired mechanicalstrength or tensile strength. Preferably the wet cement slurry, left tocure, will harden with a strength (such as compressive or tensilestrength) that increases over the curing time. However, a strength willincrease to a maximum value within a certain time of curing, forexample, within 28 days or within 7 days. In one embodiment, the wetcement slurry may be left to cure for 5 h-30 days, preferably 12 h-14days, more preferably 24 h-7 days, though in some embodiments, the wetcement slurry may be considered cured in less than 5 h or after 30 days.

In one embodiment, the cured cement material comprises zeolite clustershaving an average cluster diameter of 1-12 μm, preferably 3-10 μm, morepreferably 4-8 μm. However, in some embodiments, the cured cementmaterial may comprise zeolite clusters having an average clusterdiameter of less than 1 μm or greater than 12 μm. In an alternativeembodiment, the cured cement material may comprise dispersed zeoliteparticles that are not clustered.

In one embodiment, the zeolite clusters may be considered agglomeratesof zeolites. As used herein, the term “agglomerates” refers to aclustered particulate composition comprising primary particles, theprimary particles being aggregated together in such a way 1 o so as toform clusters thereof, at least 50 volume percent of the clusters havinga mean diameter that is at least 2 times the mean diameter of theprimary particles, and preferably at least 90 volume percent of theclusters having a mean diameter that is at least 5 times the meandiameter of the primary particles. The primary particles may be thezeolite nanoparticles having a mean diameter as previously described.

In a related embodiment, the zeolite may react with calcium hydroxide inthe cement, producing calcium silicate hydrate and calcium aluminatehydrate in the cured cement material. In the embodiments where thezeolite reacts, the unreacted zeolite may be present as zeolite clustersand may occupy pores of the cured cement material.

In one embodiment, the cured cement material further comprises pores,and a subset of the zeolite clusters is located within the pores. Thecured cement material may comprise pores having an average diameter of1-12 μm, preferably 3-10 μm, more preferably 4-8 μm, though some curedcement materials may have pores with an average pore diameter of lessthan 1 μm or greater than 12 μm. In one embodiment, the cured cementmaterial may have a hierarchical porosity, meaning that smaller poresare connected with larger pores. In one embodiment, the cured cementmaterial may have a porosity of 18-24%, preferably 20-23%, and apermeability of 0.0001-0.0010 md, preferably 0.0004-0.0006 md. In oneembodiment, the addition of zeolite nanoparticles to a wet cement slurrydecreases the porosity and permeability of a resulting cured cementmaterial. In some cases, this decrease in porosity and permeability maybe due to zeolite filling in the pores.

As mentioned previously, a subset of the zeolite clusters may be locatedwithin pores. For instance, 20-90%, preferably 30-80% of the zeoliteclusters, relative to a total number of zeolite clusters, may be locatedwithin pores. In other embodiments, less than 20% or greater than 90% ofthe zeolite clusters may be located in pores. In one embodiment, all ofthe zeolite clusters may be located within the pores.

In one embodiment, a cured cement material made with zeolitenanoparticles, or with a higher concentration of zeolite nanoparticles,may have a lower occurrence of micro cracks. The lower occurrence ofmicro cracks may be the result of a denser structure.

A cured cement material may comprise high density CSH having a C/S (i.e.calcium oxide to silica) ratio of 3.3-3.7, preferably 3.4-3.6, or about3.5. This dense CSH may be called an “inner product” and may compriseCSH in a flat, nanosheet, nanoflake, nanoplatelet, planar, or lamellarmorphology. A cured cement material may comprise low density CSH havinga C/S ratio of 3.1-3.3, preferably 3.15-3.28, or about 3.25. This lowdensity CSH may be called an “outer product” and may comprise CSH in aneedle, spike. In one embodiment, zeolite clusters may be located withinpores of high density CSH. In this embodiment, the zeolite nanoparticlesmay have reacted with the calcium hydroxide in the cement to producehigh density CSH. In another embodiment, zeolite clusters may be locatedwithin pores of low density CSH. In this embodiment, the zeolitenanoparticles may have reacted with the calcium hydroxide in the cementto produce low density CSH. In a preferred embodiment, the zeolitenanoparticles may react and produce both low density and high densityCSH in a single cured cement material. In one embodiment, CSH may existin other morphologies, such as a flower-like structure, which may beassociated with a C/S ratio of 2.8-3.1, preferably 2.85-3.05, or about3.0. In another embodiment, CSH may have a rod-like morphology rich insulfur and aluminum, suggesting a type of mineral such as Ettringite orMonosulfate.

In one embodiment, the presence of the zeolite nanoparticles makes thewet cement slurry reach a certain compressive strength in a curing timefaster than a wet cement slurry that does not comprise zeolite. Forinstance, in one embodiment, the wet cement slurry may reach acompressive strength of 2,000 psi within a time of curing which is0.8-3.0 h, preferably 1.0-2.5 h, more preferably 1.3-2.2 h faster thanan essentially identical wet cement slurry that was not formed withzeolite nanoparticles. Here, in one embodiment, the wet cement slurrymay reach a compressive strength of 2000 psi in a curing time of 5.5-8.8h, preferably 6.0-8.2 h, more preferably 6.2-7.5 h.

In a related embodiment, where the wet cement slurry comprises silicaflour and at least one additive, the wet cement slurry may reach acompressive strength of 2,000 psi within a time of curing which is1.5-3.5 h faster, preferably 1.8-3.2 h faster, more preferably 2.2-2.8 hfaster than an essentially identical wet cement slurry that was notformed with zeolite nanoparticles. Here, in one embodiment, this wetcement slurry may reach a compressive strength of 2000 psi in a curingtime of 6.0-9.0 h, preferably 6.5-8.5 h, more preferably 7.2-7.8 h.

In a further embodiment, where the wet cement slurry comprises silicaflour and at least one additive, the cured cement material has acompressive strength of 5,500-6,800 psi, preferably 5,800-6,600 psi,more preferably 5,900-6,500 psi, or about 5,900 psi, or about 6400 psi.This compressive strength may be the “unconfined compressive strength,”which is the maximum load per unit surface area a cement specimen maytake before failing in a compression test with no confining pressure. Insome embodiments, the compressive strength may be higher than 6,800 psi.In this embodiment, an essentially identical cured cement material madefrom a wet cement slurry that does not comprise zeolite may have acompressive strength of 4,500-5,500 psi, preferably 4,600-5,200 psi, orabout 5,000 psi.

In one embodiment, where the wet cement slurry comprises silica flourand at least one additive, the cured cement material may have a Young'smodulus that increases as the weight percentage of zeolite nanoparticlein the wet cement slurry increases. In this embodiment, a wet cementslurry with 0.5-1.5 wt % nanozeolite by weight of cement may form acured cement material having a Young's modulus of 1,200-1,800 MPa, orabout 1,600 MPa. A wet cement slurry with 1.5-2.5 wt % nanozeolite byweight of cement may form a cured cement material having a Young'smodulus of 1,800-2,300 MPa, or about 2,180 MPa. A wet cement slurry with2.5-3.5 wt % nanozeolite by weight of cement may form a cured cementmaterial having a Young's modulus of 2,300-2,700 MPa, or about 2,500MPa.

In one embodiment, the cured cement material may have a tensile strengthof 1,000-1,500 psi, preferably 1,100-1,450 psi, more preferably1,300-1,440 psi, or about 1400 psi. However, in some embodiments, thecured cement material may have a tensile strength of less than 1,000 psior greater than 1,500 psi.

In one embodiment, the cured cement material comprises hydrationproducts, such as calcium silicate hydrate (CSH, or C—S—H), calciumhydroxide (CH, or Portlandite), calcium silicate (for example, Larnite),aluminum calcium iron oxide (such as Ca₂FeAlO₅), and/or silicon oxide(such as silicon dioxide, or quartz). In one embodiment, the addition ofzeolite nanoparticles and/or other additives may change the compositionof hydration products in the resulting cured cement. In an alternativeembodiment, the addition of zeolite nanoparticles and/or otheradditives, for example, of certain types or of small amounts, may notchange the composition of hydration products in the resulting curedcement.

In one embodiment, the cured cement material comprises calcium silicatehydrate (CSH) at a weight percentage of 1-20 wt %, preferably 5-18 wt %,more preferably 8-17 wt %, or about 15 wt %, relative to a total weightof the cured cement material. In another embodiment, the cured cementmaterial comprises calcium silicate hydrate (CSH) at a weight percentageof 20-55 wt %, preferably 30-52 wt %, more preferably 40-48 wt % orabout 46 wt %, relative to a total weight of the cured cement material.In other embodiments, however, the cured cement material may comprisecalcium silicate hydrate at a weight percentage of less than 1 wt %, orgreater than 55 wt %, relative to a total weight of the cured cementmaterial.

In one embodiment, the cured cement material has a weight of calciumsilicate hydrate (CSH) that is 20-70% lower, preferably 30-60% lower,more preferably 35-55% lower than a second weight of calcium silicatehydrate of an essentially identical cured cement material made from awet cement slurry that does not contain zeolite nanoparticles, relativeto the second weight. For example, in one embodiment, the cured cementmaterial may comprise 5-30 wt %, preferably 10-25 wt % CSH relative to atotal weight of the cured cement material while an essentially identicalcured cement material not made with a zeolite may comprise CSH at aweight percentage of 35-55 wt %, preferably 40-45 wt % relative to atotal weight of the essentially identical cured cement material.

In one embodiment, the cured cement material comprises calcium hydroxide(CH) at a weight percentage of 35-55 wt %, preferably 38-51 wt %, morepreferably 42-48 wt %, or about 46 wt %, relative to a total weight ofthe cured cement material. In another embodiment, the cured cementmaterial comprises calcium hydroxide at a weight percentage of 8-35 wt%, preferably 14-32 wt %, more preferably 20-30 wt %, or about 28 wt %,relative to a total weight of the cured cement material. In otherembodiments, however, the cured cement material may comprise calciumhydroxide at a weight percentage of less than 8 wt %, or greater than 55wt %, relative to a total weight of the cured cement material.

In one embodiment, the cured cement material has a weight of calciumhydroxide (CH, or Portlandite) that is greater by a factor of 1.5-3.0than a second weight of calcium hydroxide of an essentially identicalcured cement material made from a wet cement slurry that does notcontain zeolite nanoparticles. For example, in one embodiment, the curedcement material may comprise 24-55 wt %, preferably 40-45 wt % CHrelative to a total weight of the cured cement material while anessentially identical cured cement material not made with a zeolite maycomprise CH at a weight percentage of 8-25 wt %, preferably 15-23 wt %relative to a total weight of the essentially identical cured cementmaterial.

In one embodiment, the cured cement material comprises calcium silicateat a weight percentage of 15-35 wt %, preferably 18-30 wt %, morepreferably 20-28 wt %, or about 24 wt %, relative to a total weight ofthe cured cement material. In another embodiment, the cured cementmaterial comprises calcium silicate at a weight percentage of 3-15 wt %,preferably 4-12 wt %, more preferably 5-9 wt %, or about 7 wt %,relative to a total weight of the cured cement material. In otherembodiments, however, the cured cement material may comprise calciumsilicate at a weight percentage of less than 3 wt %, or greater than 35wt %, relative to a total weight of the cured cement material.

In one embodiment, the cured cement material comprises aluminum calciumiron oxide at a weight percentage of 5-11 wt %, preferably 6-10.5 wt %,more preferably 8-10.2 wt %, or about 10 wt %, relative to a totalweight of the cured cement material. In another embodiment, the curedcement material comprises aluminum calcium iron oxide at a weightpercentage of 11-20 wt %, preferably 12-19 wt %, more preferably 14-18wt %, or about 16 wt %, relative to a total weight of the cured cementmaterial. In other embodiments, however, the cured cement material maycomprise aluminum calcium iron oxide at a weight percentage of less than5 wt %, or greater than 20 wt %, relative to a total weight of the curedcement material.

In one embodiment, the cured cement material comprises silicon dioxideat a weight percentage of 2-10 wt %, preferably 3-8 wt %, morepreferably 4-7 wt %, or about 5 wt %, relative to a total weight of thecured cement material. In other embodiments, however, the cured cementmaterial may comprise silicon dioxide at a weight percentage of lessthan 2 wt % (such as 0 wt %, or no silicon dioxide), or greater than 10wt %, relative to a total weight of the cured cement material.

According to a second embodiment, the present disclosure relates to acured cement material as described above, including in the first aspectof the present disclosure. In one embodiment, the cured cement materialmay be made by one of the processes described by the present disclosure.In another embodiment, the cured cement material may be made by adifferent process, either modified or completely different than theprocesses described above. The cured cement material may have mechanicaland microstructure properties that are similar or different.

The examples below are intended to further illustrate protocols forpreparing, characterizing the cured cement material, and uses thereof,and are not intended to limit the scope of the claims.

EXAMPLE 1

Procedures

The present invention relates to an oil and gas well cementingoperation, more specifically, to wells under high temperature highpressure conditions, using a cement slurry composition in which nanozeolite is used as an additive. The nano zeolite based cement slurry maybe used for primary cementing and other well completion and remedialoperations.

The present invention includes a slurry composition, comprisinghydraulic cement, water, and nano zeolite. The cement of the compositionis optionally admixed with at least one additive selected from the groupconsisting of silica flour, fluid loss control additives, retarder,expanding agent, density reducing additives, density enhancing weightingagents, friction reducing agent, defoaming agents, and combinationsthereof, for application in oil and gas well cementing under hightemperature and pressure conditions (HTPT). Thus, the cement slurrycomposition may comprise class G cement powder, nano zeolite, silicaflour, expanding agent, dispersant, fluid loss control agent, retarder,and defoamer. The slurry composition yields superior cement slurryproperties, which include thickening time, free water content,rheological properties, compressive strength, tensile strength, density,porosity and permeability.

Zeolite mineral according to Coombs et al. is a crystalline substancewith a structure characterized by a framework of linked tetrahedra, eachconsisting of four O atoms surrounding a cation. See Coombs, D. S.,Alberti, A., Armbruster, T., Artioli, G., Colella, C., Galli, E.,Vezzalini, G. (1997). Recommended nomenclature for zeolite minerals:report of the subcommittee on zeolites of the InternationalMineralogical Association, Commission on new Minerals and Mineral names.Canadian Mineralogist, 35(6), 1571-1606. doi:10.1180/minmag.1997.061.405.13—incorporated herein by reference in itsentirety. This framework contains open channels and cages. These areusually occupied by H₂O molecules and extra framework cations that arecommonly exchangeable. The channels are large enough to allow thepassage of other molecules.

Natural zeolite has a three-dimensional frame structure and isclassified as a hydrated aluminosilicate of alkali and alkaline earthcations. Zeolite crystals are characterized by a honeycomb-likestructure with extremely small pores and channels, varying in size from3×10⁻⁴-4×10⁻⁴ μm. Zeolites may be either natural or man-made and thereare more than 50 natural and 150 synthetic zeolite minerals known andused in various industries. See Ahmadi, B. and Shekarchi, M. (2010). Useof natural zeolite as a supplementary cementitious material. Cement andConcrete Composites, 32 (2), 134-141, doi:10.1016/j.cemconcomp.2009.10.006—incorporated herein by reference in itsentirety.

Natural zeolites are crystalline aluminosilicate minerals having similarchemical composition to clay minerals, but they have a three-dimensionalstructured framework in contrast to the flat layered structure of clayminerals. See Küçükyildmm, E., and B. Uzal. 2014. “Characteristics ofCalcined Natural Zeolites for Use in High-Performance Pozzolan BlendedCements,” Construction and Building Materials 73: 229-34, doi:10.1016/j.conbuildmat.2014.09.081—incorporated herein by reference inits entirety. Natural zeolites are excellent pozzolanic materials. Theirhigher external surface area and metastability is believed to be thecause of their reactivity, which complements the formation of calciumsilicate and aluminate hydrates (CSH and CAH) after the reaction withcalcium hydroxide. See Caputo, D., Liguori, B., & Colella, C. (2008).Some advances in understanding the pozzolanic activity of zeolites: Theeffect of zeolite structure. Cement and Concrete Composites, 30(5),455-462, doi: 10.1016/j.cemconcomp.2007.08.004—incorporated herein byreference in its entirety.

Natural zeolites such as Clinoptilolite and Chabazite have applicationsin various diversified fields including the cement and concreteindustry. However, natural zeolites are contaminated by other minerals,and hence they may not be suitable for several important commercialapplications where uniformity and purity are essential. Syntheticzeolites are synthesized by chemical processes, which result in a moreuniform and purer state as compared to the natural types in terms oftheir lattice structures, and sizes of pores and cages in theirframeworks. See Jha and D. N. Singh, Fly Ash Zeolites, AdvancedStructured Materials 78, doi: 10.1007/978-981-10-1404-8_2—incorporatedherein by reference in its entirety. Synthetic zeolites are created withsimilar structure as the natural zeolites and are composed ofalumino-silicate hydrates possessing the basic formula:M_(a/n)[(AlO₂)₂(SiO₂)_(b)].xH₂O,where M represents cations (like Na, K, Li, Ag, Ca, Ba etc.); nrepresents the cation valence; and x represents the moles of waterincorporated into the zeolite structure. See Luke K., Reddy R.,Fitzgerald R. M., et al. (2004). Zeolite containing cement composition.US Patent Application Publication, No. 2004-0112600—incorporated hereinby reference in its entirety.

Nano zeolite refers to nanoparticles of zeolite synthesized with samestructure as zeolites. Properties of zeolite materials are significantlychanged as particle size is decreased to nanometer scales, which resultsin improved performance as compared to their micron scale counterparts.Nanoparticles of zeolite have high surface area, which results in highersurface activity. See Tosheva Lubomira, and Valentin P. Valtchev. 2005.“Nanozeolites: Synthesis, Crystallization Mechanism, and Applications.”Chemistry of Materials. doi:10.1021/cm047908z—incorporated herein byreference in its entirety.

The term “nano zeolite” refers to particles of zeolite in which theparticle size is less than 1000 nm. In another embodiment, particle sizeis less than 100 nm. More specifically, in another embodiment, the sizeis in the range 30-80 nm, and the silica/alumina ratio may be about 2:1.

The nano zeolite used in this invention is procured from Nanoshel LLC,USA and it may be available commercially from other sources. The nanozeolite used in the current invention has an average particle size ofless than 80 nm. XRF analysis was performed to confirm the chemicalcomposition of nano zeolite used in this embodiment, which is presentedin Table 1.

TABLE 1 XRF analysis of nano zeolite used in this invention CompoundSiO₂ Al₂O₃ Fe₂O₃ CaO Total Concentration 61.30% 30.33% 1.24% 4.27%97.14%

A TEM image analysis of the nano zeolite particles used in this study isshown in FIG. 1. Here, the TEM image shows hexagonal sheet-likeparticles of nano zeolite in a size range less than 100 nm.Agglomeration of particles may be observed due to the strong attractiveforces in nanoparticles. Particle size distribution for nano zeolite asprovided by the supplier is presented in FIG. 2. All the particles havea particle size less than 100 nm, and preferably less than 80 nm.

The cement slurry in the embodiment may use fresh water or salt water insufficient quantity to produce a cement mix which may be easily pumpedto depths as far as 10,000 meters. The water to cement ratio may rangefrom about 0.5 to 0.7. In certain embodiments, it may range from 0.4 to0.5 by weight of cement.

For HPHT cementing, the cement composition in the present invention mayhave a host of different additives to impart properties to the cementslurry to ensure its pumpability, durability, and long-term integrity.The additives may include weighting agents to impart high densityrequired for balancing the formation pressure; silica flour or otherappropriate additives to ensure that long-term strength retrogression ofthe cement mix is precluded under HPHT conditions; retarders,accelerators, or friction reducing agents to ensure that the slurryremains pumpable without extensive wait on cement time; fluid lossadditives to ensure exclusion of gas migration and zonal isolationthroughout the life of the well; and dispersants to ensure the slurrystability.

The slurries are tested per the recommended practice for testing wellcements unless specified otherwise. See API RP 10B-2, RecommendedPractice for Testing Well Cements. 2013. Washington, D.C.: API,incorporated herein by reference in its entirety. API Specifications10B-2 outlines the recommended practices for slurry preparation,conditioning, and testing various properties of oil-well cement.Following API specifications makes sure that the results obtained arereproducible in the tested conditions.

A cement design of typical well in Saudi Arabia was selected to test thebehavior of nano zeolite on cement design performance. Thespecifications of selected well are presented in Table 2, and thetemperature and pressure conditions at which slurry properties areassessed are based on the selected well specifications.

TABLE 2 Specifications of selected well Well Parameters Values Depth ofwell (TVD) 14000 ft. Bottom Hole Circulating Temperature (BHCT) 228° F.Bottom Hole Static Temperature (BHST) 290° F. Time to reach bottom 49min Mud Weight (MW) 11.4 ppg Bottom Hole Pressure (BHP) 8300 psi Surfacepump pressure 1050 psiCement Slurry Preparation

The cement slurries were prepared using a variable speed high-shearblender type mixer with bottom drive blades as per the API specification(API specifications 10B, 2012). In all experiments, the wet mixingmethod has been implemented in which the cement, additives, and waterare first weighed depending on the cement design. The cement, silicaflour, and nano zeolite were blended prior to mixing with water. Bothliquid and dry additives which include fluid loss control additives,retarder, expanding agent, density reducing additives, density enhancingweighing agents, friction reducing agents, defoamer etc. were firstmixed in tap water at a low speed of 4000 rpm. The cement, silica flour,and nano zeolite dry blended mixture was subsequently added to the waterand then to the additive mixture in the blender. The whole slurry wasthen mixed at high speed of 12,000 rpm for 35 seconds. After the mixing,the cement slurry was conditioned in atmospheric consistometer atatmospheric pressure and 190° F. temperature for 30 minutes

Density

The density of cement was evaluated by using a pressurized mud balance.A pressurized mud balance removes any entrapped air and gives accuratedensity. Cement slurry is prepared according to API specifications andconditioned at 190° F. and atmospheric pressure. Conditioned slurry wasthen used for density measurement.

Free Water Content Test

The free fluid test helps determine the capacity of the cement slurry toprevent fluid separation in static conditions—both during placement, andafter the slurry has been placed into the wellbore. Excessive free fluidin the slurry may cause problems with water pockets, channeling,sedimentation, zonal isolation, etc. For the measurement of free fluidcontents, the cement slurry was prepared and conditioned at 190° F. asexplained earlier. Cement was then poured into a graduated cylinder upto the 250 mL mark, and was covered with aluminum foil to preventevaporation for 2 hours. Later, the amount of water on top was measuredin milliliters (mL).

Rheological Properties Test

Rheological properties are measured using variable speed rheometer. Theconditioned slurry is poured into the rheometer cup that waspre-conditioned at 190° F. The slurry is stirred for about 10 seconds at3 rpm, 6 rpm, 100 rpm, 200 rpm, and 300 rpm. Viscosity readings arerecorded at every speed, first in ascending order and then in descendingorder. Rheological properties including plastic viscosity (PV) and yieldpoint (YP) are calculated with Bingham Plastic model using the averageviscosity values at different speeds.

As per API specifications, gel strengths may be measured on the sameslurry after the rheology tests. The slurry was stirred for 60 s at 300rpm to make it homogenous. Then viscometer was stopped for 10 secondsand then started at 3 rpm; the maximum value recorded is called “initialgel” or “10 sec gel.” Later, the slurry was kept static for 10 minutes,and then the rheometer was started at 3 rpm. The maximum dial readingobtained here is to called the “10-minute gel.”

Thickening Time

The thickening time of cement slurry may be defined as the length oftime that the slurry will remain pumpable in well conditions. Todetermine the thickening time, the consistency of cement slurry,expressed in Bearden units of consistency (Bc), is measured using theHPHT consistometer. For the thickening time test, the slurry is notconditioned in an atmospheric consistometer. The time at which theconsistency value reached 100 Bc was considered as thickening time. Thethickening time test was performed at a temperature of 228° F. based onBHCT of the selected well and a pressure of 9400 psi. The pressure wascalculated by adding hydrostatic pressure exerted by mud column tosurface pump pressure. The time for heating rate was selected as 49minutes which is the time it would take for a cement slurry to reach thebottom of a well bore.

Static Fluid Loss Test

A fluid loss test is performed to evaluate the amount of fluid loss fromthe slurry, at given temperature and pressure conditions, usingnon-stirring fluid loss equipment. Static fluid loss test was performedat 190° F. and 1000 psi pressure as per API standards. Cement slurry isprepared and conditioned as explained earlier before subjecting it totest conditions for 30 minutes. At the end of the test, the amount ofcollected fluid loss is measured using a graduated cylinder.

Compressive Strength Test

The compressive strength is one of the most important properties ofcement, which will determine the integrity of cement and the ability ofcement sheath to resist against induced stresses over the life of awell. Two methods are employed to determine the compressive strength ofcement. The first is the non-destructive sonic determination of thecompressive strength of the cement, which uses an Ultrasonic CementAnalyzer (UCA). The second is the destructive method of UnconfinedCompressive Strength (UCS) by applying a load to square-inch cementcubes (crush strength test).

UCA gives the compressive strength development of the slurry over thetime based on the time required for the ultrasonic signal to passthrough the cement as it sets. In this method, the cement slurry wasprepared and conditioned as described earlier, and then it was kept inthe UCA for 48 hours. The temperature was raised to BHCT 228° F. in 49minutes (time to reach bottom) and then increased to BHST 290° F. in 191minutes with a pressure of 3000 psi.

The crush strength test provides the strength of a cement slurry afterit has been pumped into the well and allowed to set in staticconditions. The slurry is subjected to temperature and pressure forvarious lengths of time as per the well conditions and requirements.Cement cubes are cured using molds in a curing autoclave. Afterdemolding, the cured cubes are crushed in uniaxial crushing equipment tomeasure the maximum load the cement may bear before crushing, which isthen used to compute compressive strength. In this method, cement cubesare prepared using molds which are cured at BHST of 290° F. and pressure3000 psi for 24 hours in curing autoclave. After demolding, cured cubeswere crushed in uniaxial crushing equipment to measure unconfinedcompressive strength.

Tensile Strength Test

For tensile strength, indirect method of Splitting Tensile Strength(STS) is used in the current study as described in ASTM Standard C496.Cylinders of dimension 3 in. length and to 1.5 in. diameter (L/Dratio=2) were molded and cured for 24 hours by same pressure andtemperature schedule described for the crushing strength test. Afterremoving the cylinders from molds, small wooden strips of thickness ⅛in. and width 1 in. were placed on the top and bottom of the cylinder sothat the load would be distributed uniformly. The cylinders are placedin a horizontal direction and then crushed.

Porosity and Permeability Test

Plug samples were drilled out from untested cubes of cement. The sampleswere then end face grinded to obtain a clean parallel surface. Thesecore samples were dried under vacuum for about one day. The averagelength and diameter of the core plugs were determined from fourdifferent points along the plug. The dry weights of the core plugs wererecorded. The porosity and permeability were measured under confiningpressure of 500 psi using an automated Permeameter/Porosimeter.

The examples that follow are related to two types of cementcompositions:

-   -   EXAMPLE 2: Cement and water with nano zeolite at various        percentages.    -   EXAMPLE 3: Cement, water, nano zeolite at various percentages        together with a host of other additives used in HPHT field mixes        including silica flour, dispersant, retarder, fluid loss control        agents, expanding agent, and antifoaming agent.

EXAMPLE 2

Nano Zeolite with Class G Cement

Several tests were performed to investigate the effect of adding thenano zeolite on the properties of neat class G cement without othercement additives. The tested cement sample used in this exampleconsisted of Saudi cement type class G, nano zeolite, and water.

Cement Slurry Design

The normal slurry density of 15.8 lb/gal was used with the recommendedwater/cement ratio of 0.44 for class G cement as specified in API Spec10A. The effect of nano zeolite on various cement properties wasexamined at various nano zeolite dosages of 0-3%. The slurry compositionfor all the mix designs used in Example 2 is shown in Table 3.

TABLE 3 Cement slurry design Component Mass percentage by weight ofcement Class-G cement 100 100 100 100 Water 44 44 44 44 Nano zeolite 0 12 3 Mix design label G G1 G2 G3PV and YP of Cement Composition with Nano Zeolite

Cement rheology properties, including the plastic viscosity (PV), yieldpoint (YP), and gel strength of a cement composition, are used indescribing the quality of the final cement product and predicting itsfuture performance in a working environment, as well as its physicalproperties during and after cement processing. Cement compositions with0, 1, and 2% of nano zeolite was prepared and tested for PV and YP.Experimental results show that the addition of nano zeolite to theType-G cement mix resulted in enhancement in the rheological cementproperties such as the plastic viscosity and yield point as illustratedin Table 4. Nano zeolite caused an increase in cement solid particlesthat in turn increased the plastic viscosity and caused enhancement incement viscosity. By previous methods not using a nano zeolite,improvements in plastic viscosity and yield point have only beenminiscule. It may be concluded that rheological properties (PV and YP)of Class-G cement were improved, which would be beneficial for hightemperature wells.

Gel strength of Cement Composition with Nano Zeolite

Gel strength may be defined as a measure of the attractive forcesbetween the particles of the produced cement, which cause gelationdevelopment when the flow stops. It may also give the field operator aquick idea of cement gelation, and if there is settling within theproduced cement. It was observed that the gel strength has increasedwith increasing the amount of nano zeolite. It is obvious that theaddition of nano zeolite increases the 10-sec gel strength up to 25%with 1% nano zeolite, but the 2% nano zeolite did not cause asignificant increase as compared to 1% composition as shown in Table 4.However, when the cement slurry is subjected to a 10-min gel strengthtest, for the 1% nano zeolite mix, an almost 67% increase was observedin the 10-min gel strength as compared to the 0% nano zeolite. The10-min gel strength value for 2% nano zeolite was close to the 1% nanozeolite composition. It may be deduced that the particle suspensionability of cement slurry may be improved with nano zeolite.

TABLE 4 Effect of nano zeolite on rheological properties Rheology GelStrength Property PV, cp YP, lb/100 ft² 10-sec 10-min G 70 20 16 51 G182 24 20 85 G2 99 25 21 88Compressive Strength of Cement Composition with Nano Zeolite

Four cement systems containing nano zeolite 0, 1, 2, and 3% bwoc weretested using sonic method by ultrasonic cement analyzer (UCA) to measurethe evolution of compressive strength. Tests were conducted according tothe API specification 10B at a curing temperature of 290° F. andpressure of 3000 psi. The compressive strength of the nanozeolite cementcompositions after 6, 12, 18, 24 hours are shown in Table 5.

It may be seen from Table 3 that 1 and 2% nano zeolite slurries gavehigher strength compared to the Type-G cement mix and the cementcomposition with 3% nano zeolite. Improved early strength developmentbehavior was observed with the addition of the 2% nano zeolite. Theevolution of compressive strength over time for these cementcompositions is shown in FIG. 3.

TABLE 5 Effect of nano zeolite on compressive strength Compressivestrength, psi Time, hours G G1 G2 G3 06:00 1730 1743 1983 1554 12:002170 2180 2312 1976 18:00 2320 2337 2444 2135 24:00 2430 2546 2500 2100

The transition period between development of compressive strength of 50psi and 500 psi is important, and for well cementing it should be asshort as possible to avoid a long waiting time on cement before resumingdrilling operation. The 2% nanozeolite cement slurry has the shortesttransition time. The times to achieve 50, 500, and 2000 psi compressivestrength for the nano zeolite cement slurries are summarized in Table 6.The time to reach a compressive strength of 2000 psi is important as the2000 psi strength is considered safe for a perforation or stimulationjob. It was observed that nano zeolite slurries with 1% and 2% nanozeolite reach 2000 psi more quickly than neat class G cement. Cementcompositions with 2% nano zeolite decrease the time to reach 2000 psifrom 9 hours to 6 hours, whereas 3% nano zeolite increases the time from9 hours to 12.5 hours. A time reduction of almost 30% was observed with2% nano zeolite to reach 2000 psi. Such a reduction will help inreducing the cement waiting time.

TABLE 6 Time to gain compressive strengths of 50, 500, and 2000 psi.Compressive G G1 G2 G3 Strength (Psi) Time (Hours) 50 0.95 1.02 0.9 1.15500 1.47 1.55 1.35 1.67 2000 8.97 8.07 6.18 12.58Porosity and Permeability of Nano Zeolite Compositions

Permeability is an important property, which controls the ability of thefluid to flow at different pressures, and governs the long-termperformance of the cement sheath. The main function of the cement sheathis to seal the formation zones and stop the fluid from moving betweenthem. This may be achieved only if a lower permeability cement sheath isobtained. Porosity is also as important as permeability, and is definedas a void space in the cement sheath where fluids are stored, which atlater stages, may affect the long-term durability of the cement sheath.The porosity and permeability of cement compositions with 0, 1, and 3%nano zeolite are shown in Table 7.

Addition of nano zeolite at 1% by weight of cement (bwoc) decreases theporosity of the cement mix by 17%. However, a further increase in nanozeolite concentration increases the porosity as shown in Table 7. On theother hand, a significant reduction of 98% in the permeability resultswas observed when 1% of nano zeolite was added to the cement mix.

TABLE 7 Effect of nano zeolite on porosity and permeability PropertyPorosity, % Permeability, md G 25.76 0.3263 G1 21.48 0.0073 G3 30.310.2984Microstructural Analysis

The Scanning Electron Microscopy (SEM) of the cement mixes was carriedout to identify the composition, topography, and the pore structure ofthe final cement product. Four cement systems containing class G cement,water, and 0, 1, 2, or 3% nano zeolite were prepared and tested for themicrostructural test of SEM. FIGS. 6A, 6B, and 6C show SEM images ofhydration products with 0%, 1%, and 2% nano zeolite, respectively, curedat HPHT for 24 hours. Micro cracks are visible in the case of 0% and 1%nano zeolite slurry, as shown by the white arrows. Pore spaces aredenoted by ellipses. When 2% nano zeolite was added to the cement mix,it is evident that no micro cracks were seen in the mix. A densermicrostructure may be observed with fewer pore spaces for the 2% nanozeolite cement composition.

FIGS. 7A and 7F show magnified SEM images of hydration products with 1%and 2% nano zeolite mix, respectively, cured at HPHT for 24 hours.Unreacted particles of nano zeolite appear to be filling the pore spacesin the set cement, which unreacted particles are highlighted by whitecircles. The lower left white circle of FIG. 7A is magnified in FIG. 7BThese SEM images confirm that nano zeolite is acting as a nano-filler inthe cement matrix. As a result, these images provide the densemicrostructure which is evident from SEM images. The hydration productsare further modified with the increase in nano zeolite concentration. Ascompared to 1% nano zeolite, the 2% nano zeolite sample (FIG. 7F) hasvery few unreacted particles.

The nano zeolite particles act as nucleation sites on which outer CSHparticles grow. Nano zeolite particles connected with growth of CSH maybe seen in FIG. 7F. Here, the circled areas show the unreacted nanozeolite, which is present at a lower amount than the unreacted nanozeolite of FIG. 7A. In FIG. 7F, the “2” label marks the outer CSH, whichis the CSH growing on nano zeolite particles by the nucleation sitephenomena.

The compressive strength results of 1% and 2% nano zeolite slurries at24 hours are similar, but the enhancement in early strength is greaterin the case of the 2% nano zeolite slurry. This observation is alsovalidated from the SEM images. Nano zeolite acting as a nucleation sitefor CSH growth is believed to be the cause of improved early compressivestrength.

EXAMPLE 3

Nano Zeolite with Class G Cement, Silica Flour, and Additives

Several tests were performed to investigate the effect of adding thenano zeolite on the properties of API class G cement with other cementadditives to simulate the conditions in a HPHT well. The specimenstested in Example 3 comprise cement type class G, silica flour, cementadditives, nano zeolite, and water.

Cement Slurry Design

The chosen well requires a special cement system design since this wellis 14,000 ft deep with high pressure and temperature conditions. Theselected cement system comprises different additives in which eachmaterial contributes and adds chemical and physical properties to makethe cementing job successful. Table 8 explains the cement slurry designstested in this example. The cement composition comprises Cement Type-G,silica flour, expanding agent, dispersant, two types of fluid losscontrol agents, retarder, water, and nano zeolite at 0, 1, 2, and 3%bwoc. The base mix (BM) with no nanozeolite additive serves to comparethe performance of cement compositions with nanozeolites. The water tocement ratio of the cement mixes was kept constant at 0.44. A largepercentage of silica flour, 35% bwoc, was used to prevent strengthretrogression at high temperature conditions observed in deep wells incement compositions without silica flour. The slurry used in thisexample has a 16.8 ppg density.

TABLE 8 Cement slurry design Component Mass percentage by weight ofcement (bwoc) Cement 100 100 100 100 Water 44 44 44 44 Silica flour 3535 35 35 Expanding agent 1 1 1 1 Dispersant 1 1 1 1 Fluid loss controlagent 0.2 0.2 0.2 0.2 Fluid loss control agent 0.5 0.5 0.5 0.5 Retarder0.7 0.7 0.7 0.7 Nano zeolite 0 1 2 3 Mix design label BM NZ1 NZ2 NZ3Effect of Nano Zeolite on Density

The density of cement is critical in drilling and cementing of wells. Itmay result in either destroying the well formation, or leading to wellblowout, especially when cementing deep wells where high density isrequired. Cement systems with percentages of nano zeolite of 0, 1, 2,and 3% bwoc were prepared, and the density of the produced cement wasmeasured using a pressurized cement balance. Admixing nano zeolite withthe cement does not influence density of the cement mix. Both thecontrol mix or the base mix (BM) and the nano zeolite based cementcompositions have almost the same density as shown in the Table 9.

Effect of Nano Zeolite on Free Water Content

Water is added to the cement at a fixed water cement ratio to give thecement its appropriate density. If excessive amounts of water added tothe cement, water will accumulate at the top, and the cement settles atthe bottom. Cement systems with 0, 1, 2, and 3% of nano zeolite wereprepared and tested for the free water separation. The addition of nanozeolite to the cement slurry resulted in no free water separation at thetop of the cement as observed in Table 9.

TABLE 9 Effect of nano zeolite on density and free water PropertyDensity, lb/gal Free water, mL/250 mL BM 16.8 0 NZ1 16.95 0 NZ2 16.85 0NZ3 16.9 0Effect of Nano Zeolite on Rheological Properties

Cement compositions with 0, 1, 2, and 3% of nano zeolite were preparedand tested for cement rheological properties including plasticviscosity, yield point, and gel strength. The variability of therheological properties with different nano zeolite amounts is presentedin Table 10. Addition of nano zeolite resulted in an increase in plasticviscosity, which may be attributed to an increase in solid particles.This enhancement makes nano zeolite a good viscosifier, and helps inefficient mud displacement especially in high temperature wells. Theyield point was not affected significantly. It is desirable for thecement slurry to have low yield points. The nano zeolite additionimproved the 10-min gel strength of cement slurry, as summarized inTable 10, which indicates a better particle suspending ability of cementslurries with nano zeolite.

TABLE 10 Effect of nano zeolite on rheological properties Rheology GelStrength Property PV, cp YP, lb/100 ft² 10-sec 10 min BM 232 4 6 19 NZ1264 4 6 21 NZ2 272 4 7 25 NZ3 275 7 7 26Effect of Nano Zeolite on Thickening Time

The thickening times of cement samples containing of 0, 1, 2, and 3%nano zeolite under HPHT conditions were determined to investigate if thenanozeolite has a retarding or an accelerating effect on thickening. Thethickening time of cement helps to determining the suitability of usingthe cement in different work circumstances. The addition of nano zeoliteto the cement resulted in a slight increase in the thickening time ofthe cement compositions as shown in Table 11. Nano zeolite slows thehydration reaction (35 minutes in case of 3% nano zeolite), which mayhave some advantages in the case of cementing deep wells. Comparison ofthickening time behavior of all slurries tested is also presented inFIG. 5.

Effect of Nano Zeolite on Fluid Loss

The effect of nano zeolite on fluid loss of cement compositionscontaining 0, 1, 2, and 3% nano zeolite as per API specifications isshown in Table 11. The purpose of the fluid loss test is to measure theamount of the fluid lost when the cement is subjected to a differentialpressure within the well. Most of the cement losses occur during thecementing of a formation having a high permeability or sensitivity.Measured fluid loss of all cement slurries are less than 50 mL per 30min which is good in case of both liner cementing and horizontal wellcementing. The measured fluid loss was also good for preventing gaschanneling as recommended by Al-Yami et al. See Al-Yami, A. S. (2015).An Overview of Different Chemicals Used in Designing Cement Slurries forOil and Gas Wells. Society of Petroleum Engineers. DOI:10.2118/175259-MS, incorporated herein by reference in its entirety.

TABLE 11 Effect of nano zeolite on thickening time and fluid lossThickening Fluid loss Property Time, hours (API), mL BM 4:46 32 NZ1 4:5440 NZ2 5:05 30 NZ3 5:20 40Ultrasonic Compressive Strength of Nano Zeolite Cement Mixes

Cement systems containing nano zeolite at 0, 1, 2, and 3% bwoc weretested for evolution of compressive strength by sonic method (UCA).Tests were conducted according to the temperature and pressureconditions described earlier. The compressive strength of the cementsamples is reported after 6, 12, 18, 24, and 48 hours as shown in Table12. It is clear that 2% nano zeolite gave the highest strength comparedto all other mixes. High early strength development was observed withthe addition of the 2% nano zeolite, which helps in reducing the waitingon cement time, and as a result, it reduces the cost of the cementingjob. The highest compressive strength achieved by sonic method was withthe 2% nano zeolite sample; after 48 hours of the curing process, thissample had a compressive strength around 6300 psi, which is 5% greaterthan the BM sample. The compressive strength development over time forthe different cement compositions is shown in FIG. 4.

TABLE 12 Effect of nano zeolite on compressive strength (sonic method)Compressive strength, psi Time, hours BM NZ1 NZ2 NZ3 06:00 1690 15001858 1693 12:00 2223 2261 2685 2529 18:00 4245 4342 4153 4143 24:00 54345557 5435 5106 48:00 6019 6007 6325 6013

The time for the slurries to achieve compressive strengths of 50, 500,and 2000 psi are summarized in Table 13. The time to reach a strength of2000 psi is important, as this strength is considered a safe level for aperforation or stimulation job. It was observed that nano zeoliteslurries have a shorter time required to reach 2000 psi as compared tothe base mix. Rapid and early strength development was achieved with 2%nano zeolite, for instance, the 2000 psi strength level was reachedafter 6.45 hours, which is considerably faster than the base mix withoutthe addition of nano zeolite (9.35 hours).

TABLE 13 Time to gain compressive strengths (50, 500, and 2000 psi)Compressive BM NZ1 NZ2 NZ3 Strength (psi) Time (Hours) 50 3.73 4.12 3.943.62 500 4.25 4.7 4.44 4.22 2000 9.35 8.75 6.45 7.58Crushing Strength and Modulus of Elasticity

Unconfined compressive strength (UCS) is the maximum load per unitsurface area a cement specimen may take before failing in a compressiontest with no confining pressure. Results of UCS tests for thenanozeolite cement compositions are presented in Table 14. It isobserved that nano zeolite increases the compressive strength of cementmixes. At 1% nano zeolite, the crushing strength is of the same order asthe control mix. However, with 2% nano zeolite cement composition thecompressive strength at macro scale increases by about 20% and at 3% itis about 28% higher.

TABLE 14 Effect of nano zeolite on unconfined compressive strengthSample BM NZ1 NZ2 NZ3 1 5000 4800 5550 6450 2 — 5100 6400 6350 Average(Psi) 5000 4950 5975 6400

Young's modulus results are shown in Table 15, which indicates theincrease of Young's modulus with the addition of nano zeolite. A higherYoung's modulus indicates set cement samples that have a higherstiffness.

TABLE 15 Effect of nano zeolite on Young's modulus NZ1 NZ2 NZ3 Young'sModulus (MPa) 1653 2179 2525Effect of Namo Zeolite on Tensile Strength

If there are enough induced stresses to cause mechanical failure,tensile failure is more likely to happen than compressive failure. Thus,the evaluation of tensile strength is critical for engineers to assessthe failure criteria for set cements. See Heinold, T., Dillenbeck, R.,Bray, W. et al. 2003. Analysis of Tensile Strength Test Methodologiesfor Evaluating Oil and Gas Well Cement Systems. Presented at the SPEAnnual Technical Conference & Exhibition, Denver, Colo., 5-8 October.SPE-84565-MS, incorporated herein by reference in its entirety. Theresults of tensile strength tests for nano zeolite cement slurries aregiven in Table 16. There was no specific trend with the increase inconcentration of nano zeolite. The tensile strength of nano zeoliteincreased with the 1% addition of nano zeolite but then decreased withthe 2% nano zeolite concentration. The tensile strength of the 3% nanozeolite cement mix was similar to the 1% nano zeolite slurry.

TABLE 16 Effect of nano zeolite on tensile strength Sample BM NZ1 NZ2NZ3 1 1100 1450 1050 1400 2 1350 1350 — — Average (psi) 1225 1400 10501400Effect of Nano Zeolite on Porosity and Permeability

The addition of nano zeolite decreased the porosity and permeability ofnano zeolite cement mixes as shown in Table 17. This table shows thatthe 0% NZ cement slurry had a very low permeability, and that theaddition of nano zeolite further reduced the permeability. The cementcomposition having 1% nano zeolite decreased the porosity slightly belowthe base mix, but increasing the nano zeolite concentration to 2%increased the porosity. Nano zeolite caused a considerable decrease of44% and 55% in permeability with 1% and 2% nano zeolite concentrations,both compared to the base mix, respectively, indicating the effect ofthe nano zeolite to fill empty pores.

TABLE 17 Effect of nano zeolite on porosity and permeability PropertyPorosity, % Permeability, md BM 21.57 0.0009 NZ1 20.51 0.0005 NZ2 23.350.0004

EXAMPLE 4

Microstructure

Effective dispersion to avoid nanoparticles agglomeration is the key inimproving the microstructure and strength of the cement withnanoparticles. Otherwise, inclusion of nanomaterials may negativelyaffect the cement properties. Such negative effects may arise withexcess nanomaterials, which may agglomerate and produce weak zones thathave a significant influence on the bulk material strength. XRD issemi-quantitative analysis, so the percentages given may be approximate,but the trend will be according to the peaks of different crystallinematerials observed in the mix. The levels of hydration products in thedifferent cement mixes as estimated by XRD are shown in Table 18.

Nano zeolite reacts with calcium hydroxide (CH), producing calciumsilicate hydrates (C—S—H), thus the voids and pores of the cement thatreceive the nano zeolite contain some amount of CSH product.

As observed by the SEM images, the unreacted nano zeolite increases withthe percent addition of nanozeolite in the cement mix. Table 18 showsthat the percentage of CSH decreases from 50% (G1) to 15% (G3) as theamount of nano zeolite increases. The table also shows that Portlandite(CH) increases from 10%, to 28%, to 46% as the nano zeolite is increasedgoing from G1 to G2 to G3.

It may be observed that for the G3 sample, the concentration of calciumsilicate hydrate (CSH) was reduced significantly while the Portlandite(CH) increased. The CSH levels for the G1 and G2 mixes are higher thanfor the G mix. These results are in line with the compressive strengthresults. Higher CSH concentrations are correlated with higher strengthand vice versa. Some unreacted silica is also present in the case ofhigher concentrations of nano zeolite. The amount of unreactednanozeolite particles cannot be precisely calculated, but the abovevalues indicate its presence in the cement.

TABLE 18 Hydration Products Hydration products G G1 G2 G3 CalciumSilicate Hydrate (CSH) 43% 50% 46% 15% Calcium silicate (Larnite) 26%24%  7% 24% Calcium Hydroxide (CH, Portlandite) 19% 10% 28% 46% AluminumCalcium Iron Oxide (Ca₂FeAlO₅) 12% 16% 15% 10% Silicon oxide (Quartz) 0%  0%  4%  5%

FIGS. 7A and 7B are SEM images magnified to analyze the smallerparticles, which appear to be unreacted nano zeolite particlesagglomerated in the mix. These particles are highlighted by whitecircles as seen in FIG. 7A.

FIG. 7B shows the particle size of smaller particles as estimated by atool provided in EDS analysis software. The particle size of range400-600 nm may be seen. In addition, the SEM analysis of nano zeolitegave a similar particle size range of 400-600 nm, indicating theagglomeration of particles (see FIG. 7E).

EDS analysis at different locations is summarized in FIGS. 7C and 7D.Location selected as Spectrum 18 (location shown in FIG. 7B, spectrumshown in FIG. 7C) indicates the high density CSH which is also called asinner product, EDS analysis shows the presence of silica with C/S=3.5.On the other hand, Spectrum 20 (location shown in FIG. 7B, spectrumshown in FIG. 7D) shows the needle like, low density CSH, which istermed as outer product CSH. EDS analysis indicated the C/S ratio of3.25. It appears that nano zeolite particles are filling the pore spacebetween both high and low density CSH.

SEM analysis of G2 mix with 2% nano zeolite (FIG. 6C) shows no evidenceof micro cracks, unlike the G and G1 mixes. G2 appears to be the densestmix among all samples. It may be seen that as the nano zeoliteconcentration is increased, hydration products are further modified,which may include reducing micro cracks.

From FIG. 7F, it may be observed that there are some unreacted nanozeolite particles left in the mix as highlighted by the white circles,and similar in appearance to the unreacted nano zeolite in the G1 sample(FIG. 7A). However, the amount of unreacted particle is very low in theG2 mix as compared to the G1 mix. It appears that the nano zeoliteparticles acted as nucleation sites on which outer CSH particles couldgrow. The magnified image at the same area is presented in FIG. 7F,which confirms nano zeolite acting as nucleation sites as the imageshows nano zeolite particles connected with the growth of CSH. Thecompressive strength results of samples G and G2, as listed in Table 5,show that G2 has an early strength enhancement, but at 24 hours, has anequivalent compressive strength as G1. This observation also validatesthe nucleation site phenomenon as observed in SEM images.

SEM and EDS analysis of G3 mix shows that the mix G3 slurry with 3%Nanozeolite is completely different from what was seen in the other Gmixes. The SEM of the G3 mix is shown in FIG. 8A, and the EDS analysis(from Spectrum 36 and Spectrum 37 within FIG. 8A) is shown in FIGS. 8Band 8C.

Flower-like structures are located throughout the mixture and appear tobe an agglomeration of smaller rod-like structures. EDS measurement ofthese rod-like structures (Spectrum 36 and Spectrum 37, in FIGS. 8B and8C, respectively) show them to be rich in sulphur and aluminum, whichsuggests some form of ettringite or monosulfate. The significantdecrease of G3 mix compressive strength (as shown in Table 5) alsoconfirms the formation of sulfate. These results may also be validatedby the significant increases in porosity and permeability as compared tothe G1 slurry. The EDS of a flower-like structure revealed some form ofCSH with a C/S ratio of 3.

To summarize the results of microstructural analysis, the followingconclusions may be made:

-   -   The addition of nano zeolite modified the cement hydration        products as compared to the neat Class G slurry.    -   From the SEM images of G and G1 cement slurries, micro cracks        are evident, which may be attributed to the strength        retrogression at high temperatures. However, as the        concentration of nano zeolite increased, micro cracks were no        longer observed.    -   Both inner product and outer product CSH (high density and low        density) were observed in G1 mix, implying the effect of nano        zeolite particles on cement hydration.    -   From the SEM image of G1, agglomeration of nanomaterial may be        seen in pore spaces, which confirms the nano-filler effect of        the nano zeolite. Porosity and permeability results also        validated the nano-filler effect, as G1 had significantly lower        porosity and permeability values.

In addition, it is observed that there may be a need for effectivedispersion of nano zeolite particles as many of them agglomerated insome pore spaces while other pore spaces were left open. This explainswhy significant reductions in porosity and permeability did not alwayscorrelate with higher compressive strength.

The invention claimed is:
 1. A method of making and curing a wet cementslurry to form a cured cement material, comprising: mixing a hydrauliccement; water and/or brine in an amount of 40-50% by weight of thehydraulic cement; 0.5-4 wt % zeolite nanoparticles by weight of thehydraulic cement, and 0.8-1.2 wt % of a dispersant by weight of thehydraulic cement to form the wet cement slurry; and curing the wetcement slurry to produce the cured cement material, wherein the curedcement material comprises zeolite clusters having an average clusterdiameter of 1-12 μm, wherein the zeolite nanoparticles have an averagediameter of 40-100 nm, wherein the cured cement material is porous, withpores having an average diameter of 1-12 μm, and wherein a subset of thezeolite clusters is located within the pores.
 2. The method of claim 1,wherein the hydraulic cement is selected from the group consisting of anAPI Class A Portland cement, an API Class G Portland cement, an APIClass H Portland cement, and a Saudi Class G hydraulic cement.
 3. Themethod of claim 1, wherein the zeolite nanoparticles have a silica toalumina mass ratio of 1.2:1-3.0:1.
 4. The method of claim 1, wherein thezeolite nanoparticles comprise 1-6 wt % CaO relative to a total weightof the zeolite nanoparticles.
 5. The method of claim 1, wherein the wetcement slurry reaches a compressive strength of 2,000 psi within a timeof curing which is 0.8-3.0 h faster than an essentially identical wetcement slurry that was not formed with zeolite nanoparticles.
 6. Themethod of claim 1, wherein the wet cement slurry further comprises atleast one additive selected from the group consisting of an expandingagent, a fluid loss control agent, a retarder, a defoamer, a densityreducing additive, a density enhancing weighting agent, a foaming agent,and a friction reducing agent.
 7. The method of claim 6, wherein thecured cement material has a compressive strength of 5,500-6,800 psi. 8.The method of claim 6, wherein the wet cement slurry reaches acompressive strength of 2,000 psi within a time of curing which is1.5-3.5 h faster than an essentially identical wet cement slurry thatwas not formed with zeolite nanoparticles.
 9. The method of claim 1,wherein the cured cement material has a weight of calcium silicatehydrate that is 20-70% lower than a second weight of calcium silicatehydrate of an essentially identical cured cement material made from awet cement slurry that does not contain zeolite nanoparticles, relativeto the second weight.
 10. The method of claim 1, wherein the curedcement material has a weight of calcium hydroxide that is greater by afactor of 1.5-3.0 than a second weight of calcium hydroxide of anessentially identical cured cement material made from a wet cementslurry that does not contain zeolite nanoparticles.